Poor Kourtney. She’s been trying to appear level-headed amidst rumors that Kendall and Scott hooked up, but HollywoodLife.com has EXCLUSIVELY learned that the rumors are incredibly ‘stressful’ to her — and that she’s actually freaking out.

Kourtney Kardashian, 35, doesn’t necessarily believe that Scott Disick, 31, and Kendall Jenner, 19, have been hooking up. But that doesn’t mean the rumors aren’t getting to her head. The KUWTK star is dealing with demons of her own amidst the hookup rumors, because they all lead back to one thing — trust issues with Scott. Here’s what we know!

“Kourtney is dealing with her own self-esteem issues, she’s getting older and she’s had three kids, her body is not the same as it was when she was 21 so when she sees Scott checking out younger girls or even when she thinks about it she gets upset,” a source tells HollywoodLife.com EXCLUSIVELY.

“She’s always had jealousy issues with Scott but the older she gets, the harder it is to deal with,” our insider adds. “Having Scott leave her for a younger model is her worst nightmare.”

Poor Kourtney! We can imagine it doesn’t feel good to see Scott out partying with Kendall and her friends. Plus, you would think the father of three would want to spend time with his family! His constant partying leads her to have these intense feeling of insecurity, and we don’t blame her. As we told you, her jealousy is so intense, that she sometimes worries that Scott would hook up with one of her younger sisters.

“She’s not blaming Kendall though and she doesn’t want her to feel bad, that’s why she’s telling her she thinks it’s funny she doesn’t want her to think she’s done anything wrong because she hasn’t,” our source continues. “It’s got nothing to do with Kendall, it’s Scott that she’s mad at. Whenever she gets upset over this, even if it’s because of a bad dream or something she takes it out on Scott and he kind of deserves it.”

Kourtney does know deep down that the affair between Scott and Kendall is just a rumor, even though it’s incredibly “stressful” on her. But where she’s coming from isn’t crazy — Scott has partied a ton with Kendall and her young, hot model friends, we EXCLUSIVELY learned.

“There was even one night were he went out all night with them, he didn’t get home until the sun was up, she was home with the kids and he was partying with girls in their 20’s,” our insider dished. “That is another huge sore spot, they had a huge fight over that and this story is dragging it all up again.”

What do YOU think, HollywoodLifers? Do you think Kourtney should be bothered by rumors of Scott and Kendall hooking up? Sound off below!